eCompass

A compass to keep you on the right track.

🛆 eCompass Chip

An eCompass is a tilt compensated electronic compass utilizing an accelerometer and a magnetometer. Those from ST Microelectronics provide very accurate acceleration and guidance. Having already worked with the LSM303AGR in the past, this is the solution I opted for.

ST's module offers a very low power system for very high performance. Its accelerometer coupled with a magnetometer, all in a 4mm^2 package, makes it a real eye-catcher.

The LSM303AGR is polyvalent: it can detect movement, provide orientation information, assist in dead-reckoning and much more. It's the perfect compass for the project.

LSM303AGR from ST Microelectronics

Technological Capabilities

Characteristic	Description
Package	LGA-12 | 2x2x1mm
Acceleration Features	3 axes (X/Y/Z) ±2 / ±4 / ±8 / ±16g selectable full scales Avg of 3.7µA power consumption
Magnetic Features	3 magnetic field channels (X/Y/Z) ±50 gauss magnetic dynamic range Avg of 200µA power consumption
Resolution	16-bit data output
Speed Mode	100kHz, 400kHz, 1MHz, 3.4MHz
Operating Temperature	-40°C ti +85°C
Current consumption in power-down mode	~2µA

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🛆 Hardware Integration

To integrate this component, simply refer to the datasheet. Pin n°5 is connected to ground via a 220nF capacitor. The eCompass is supplied in 3.3V with three decoupling capacitors (see page 35 of the datasheet).

Kicad | eCompass

Pin Number	Symbol	Description
1	SCL SPC	I2C serial clock SPI serial port clock
2	CS_ACC	Accelerometer: SPI enable I2C/SPI mode selection
3	CS_MAG	Magnetometer: SPI enable I2C/SPI mode selection
4	SDA SDI SDO	I2C serial data (SDA) SPI serial data input (SDI) 3-wire interface serial data output (SDO)
5	C1	Capacitor connection (C1 = 220 nF)
6 & 8	GND	Connected to GND
7	INT_MAG DRDY	Magnetometer interrupt Data-ready signal
9	Vdd	Power supply
10	Vdd_IO	Power supply for I/O pins
11	INT_2_XL	Accelerometer interrupt 2
12	INT_1_XL	Accelerometer interrupt 1

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🛆 Documentation

LSM303AGR | Product - STMicroelectronicsSTMicroelectronics

Web Site | LSM303AGR

2MB

SensoreCompas_LSM303AGR.pdf

PDF

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Datasheet | LSM303AGR